This invention is directed to a method for preventing or minimizing the effects of a drug on an embryo or a fetus by placental transport while alleviating pain and anxiety of the pregnant female during such pregnancy.
It has long been recognized that analgesics, at best, have limited use for women at all stages of pregnancy including labor and delivery. This limitation is due to the recognized transfer of the analgesic across the placental barrier with resultant potential detremental effect on the developing embryo or fetus. In addition, during labor, placental transport can produce depression of respiration of the newborn.
Thus, in the 1982 Physician's Desk Reference, 36th Edition, pp. 2025-2026, the following is stated with respect to meperidine:
Meperidine should not be used in pregnant women prior to the labor period, unless in the judgment of the physician the potential benefits outweigh the possible hazards, because safe use in pregnancy prior to labor has not been established relative to possible adverse effects on fetal development. PA1 When used as an obstetrical analgesic, meperidine crosses the placental barrier and can produce depression of respiration and psychophysiologic functions in the newborn. Resuscitation may be required.
It has now been discovered that a particular pentapeptide having analgesic properties is highly advantageous in the treatment of pain and anxiety in pregnant women since it exhibits negligible, if any, transport across the placental barrier. The compound, metkephamid, has the structure EQU H-L-Tyr-D-Ala-Gly-L-Phe-L-(N-CH.sub.3)Met-NH.sub.2
and is covered by U.S. Pat. No. 4,322,342. It is to the use of this compound and pharmaceutically acceptable salts thereof that this invention is directed.